The present invention relates to an actuator and, more particularly, to an actuator that incorporates the use of shape memory wires and that is particularly suitable for use in a valve.
Shape memory wires or “muscle wires” contract when heated; however, when shape memory wires are subjected to constant or increasing loads during their contraction their strokes will be limited or their size will need to be increased in order to prevent the stresses in the wires from exceeding the wire failure stress. As a result, their use in certain applications has been limited.
Accordingly there is a need for an actuator that can take advantage of the properties of shape memory wires and yet avoid their inherent limitations.